The present invention relates to an ink fountain apparatus for a rotary printing press, which stores ink to be supplied to a plate surface and, more particularly, to an ink fountain apparatus for a rotary printing press, which has intermediate ink dams arranged between a pair of opposing ink dams.
When printing is to be performed with a rotary printing press, the plate sometimes has a pattern at only its portion in the entire width depending on the specifications of the printing products. In this case, if ink is stored in the entire ink fountain and printing is performed, the ink may be wasted. For this reason, intermediate ink dams are formed on two sides of a portion corresponding to the pattern, and the ink is stored in only inside the intermediate ink dams. In rainbow printing wherein inks of different colors are supplied to appropriate portions in the entire length of the plate cylinder and several colors are printed at once, intermediate ink dams are provided so that adjacent inks do not mix with each other.
As disclosed in U.S. patent application No. 2003/0164104, a conventional intermediate ink dam includes a press plate made of an elastic material which has a fountain press portion for pressing the outer surface of a fountain roller, and a blade press portion for pressing a fountain blade. A press means presses this press plate toward the fountain roller and the fountain blade, simultaneously.
In the above conventional ink fountain apparatus for the rotary printing press, when the plurality of intermediate ink dams are arranged, the press forces of the press means must be large in order to suppress variations between the press forces of the press plates of the respective intermediate ink dams. For this reason, since the fountain roller is flexed by an overload applied from the press plates to the outer surface of the fountain roller, an ink film with an appropriate film thickness cannot be formed on the outer surface of the fountain roller, thus posing a problem. Also, the overload is applied to the fountain roller because a contact resistance between the press plates and the fountain roller is made large by the overload, and a rotational driving system of the fountain roller is braked, thus posing a problem.
Also, in the conventional ink fountain apparatus for the rotary printing press, if the width of the fountain press portion of the press plate is made small, inks mix with each other when attaching the intermediate ink dam for the fountain roller not perpendicularly but slantly. Therefore, the width of the fountain press portion must be large to some degree. Alternatively, if the width of the fountain press portion is made large, a press surface with the large width stops supplying the ink downstream of the fountain roller. For this reason, the press force of the press means must be made large, thus posing the same problem as described above.